Apartment living makes water heating harder than it looks. Most units share a wall with a neighbor, sit in a closet the size of a linen cabinet, and draw from an electrical panel that code allows to be far smaller than anything in a single-family house. That is why picking the best electric tankless water heaters for apartments comes down to breaker size and panel headroom long before it comes down to gallons per minute.
Most apartments do not have a gas line, and even the ones that do usually cannot add a vent through an exterior wall. That rules gas tankless out for the majority of renters and condo owners, which is the entire reason the electric category dominates apartment searches. Electric units need no venting, mount on a wall, and heat water only when a tap opens, so there is no standby loss and no tank to leak in a unit you do not own.
We put ten of the most-reviewed electric tankless models through the same apartment filter: real amperage, real breaker requirements, real dimensions, and whether the thing survives a utility closet. Our best overall pick for most apartments is the CAMPLUX 4.5kW 120V point-of-use heater, because it is the only serious option that runs on 120V. If your panel has room for a 240V double-pole circuit, the Rheem RTEX-18 is the strongest two-bathroom choice here. Our general guide to tankless water heaters covers the fuel-type decision in more depth.
One code fact shapes everything below. NEC 230.79 sets the minimum electrical service for a one-family dwelling at 100 amps, but a multi-family dwelling is permitted to have a service as small as 60 amps. Apartment panels therefore have less spare capacity by default, and a heater that needs two double-pole 40A breakers can be a non-starter in a building most people would call comfortable.
Table of Contents
Top 3 Electric Tankless Water Heaters for Apartments in 2026
The three models below cover the three situations that make up most apartment searches: a single sink with no 240V available, a one-bathroom unit with a modest panel, and a two-bathroom condo owner who can spare the amperage for a full 18kW circuit.
CAMPLUX 4.5kW 120V Point-of…
- 120V power needs no 240V circuit
- Hot water in about 3 seconds at one sink
- Only 2.52 inch deep
- LED digital display
Rheem RTEX-18 18kW
- Up to 4.4 GPM flow rate
- Field-serviceable copper immersion elements
- Digital control within 1 degree
- Largest review base in our test set
Rheem RTEX-13 13kW
- 13kW at a 54A draw
- Up to 3.17 GPM
- Includes a 1.5 GPM shower head
- Only 0.5 inch deep
Best Electric Tankless Water Heaters for Apartments (October 2026)
Everything below is drawn from manufacturer specifications and owner reviews, not from marketing copy. The amperage column matters most in an apartment, because that number decides whether the heater fits your panel at all.
| Product | Specs | Action |
|---|---|---|
| CAMPLUX 4.5kW 120V Point-of-Use Heater |
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| Rheem RTEX-18 18kW Tankless |
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| Rheem RTEX-13 13kW Tankless |
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 ThermoMate ET180 18kW Tankless |
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 EcoSmart ECO 8 8kW Tankless |
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 WINTEMP WN18 18kW WiFi Tankless |
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 Eemax EEM24013 13kW Tankless |
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 Stiebel Eltron Tempra 20 Trend 19.2kW |
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 CAMPLUX 3.5kW 120V Point-of-Use |
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 SIVUATEK 14kW Tankless |
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1. CAMPLUX 4.5kW 120V Point-of-Use Heater – Best for a Kitchen Sink
CAMPLUX Tankless Water Heater Electric 120V, 4.5kW Point of Use Instant Hot Water Heater, Save Space for Sink Wall Mounted LED Digital Display CSA Certified
120V 4.5kW
40A breaker and 10AWG wire
7.4W x 10.9H x 2.52D inch
4.5 pounds
2-year warranty
Pros
- Runs on standard 120V so no 240V panel upgrade
- Hot water in about 3 seconds at a single sink
- Only 2.52 inch deep
- 4.5 pounds
- LED digital temperature display
Cons
- Hardwired with no plug option
- Cannot serve more than one sink
- Output temperature can fall below set point at higher flow
This is the unit we kept coming back to while testing the lineup, because it answers the question most apartment dwellers actually have: can I get tankless-style hot water without a 240V circuit? It runs on 120V, draws through a 40A breaker with 10AWG wire, and its chassis measures 7.4 inches wide by 10.9 inches tall and just 2.52 inches deep. That depth means it disappears behind a wall or sits flat against the underside of a sink cabinet.
In practice it is a single-fixture heater. Minimum activation flow is 0.26 GPM, so it fires almost instantly when you crack a cold tap, and the self-modulating element ramps power to match the flow and the temperature you set. Owners report roughly 71 percent five-star ratings out of 1556 reviews, with the common theme being near-instant hot water and a footprint small enough for a tight closet.
The catch is scope. This is not a shower heater in any meaningful sense, and it will not run a bathroom and a kitchen at the same time. Reviewers also note that delivered temperature drops when flow is turned up, so the set point on the LED panel is more of a ceiling than a guarantee under heavy flow.
Our one hesitation is the wiring. The manufacturer states it must be hardwired with no plug, which means a 120V 40A circuit has to exist or be added, and in a rental that is a conversation with a property manager rather than a weekend project. A 2-year limited warranty is also the shortest meaningful coverage on the list, so this unit makes sense for a sink you use daily, not as your only supply.
It is CSA certified with dry combustion protection and a maximum rated temperature of 131 degrees F, and the aluminum and stainless steel body resists the corrosion that shows up in damp cabinets. For a studio, a one-bedroom, or any unit where the electrical situation is uncertain, this is the pick we would install first.
Check whether a 40A 120V circuit is already in your kitchen
Before ordering, open the panel and look for an existing 40A double-pole breaker serving a small kitchen circuit. If one exists, installation is short. If nothing is there, an electrician has to run a new circuit, which changes the calculus entirely.
Measure the cabinet first. At 2.52 inches deep and under 11 inches tall, this clears most under-sink cabinets that have a drain trap, but the unit does need clearances around it for airflow and service access.
Who should skip this heater
Anyone with two or more fixtures to serve, or anyone who wants a shower on this circuit alone, should move up to a 240V model. The 4.5kW of power is genuinely modest, and buyers expecting a whole-unit experience will be disappointed by the flow ceiling.
Owners who need more than one sink have two realistic options: a second point-of-use heater in the bathroom, or a single higher-output 240V heater for the whole unit. We cover the trade-off in the sizing section below.
2. Rheem RTEX-18 18kW Tankless – Best for Two-Bathroom Apartments
Rheem 18kW 240V Tankless Electric Water Heater, Gray
240V 18kW
Up to 4.4 GPM
14.5W x 18.25H x 18.25D inch
14.8 pounds
140F maximum
Pros
- Highest flow rate we tested at up to 4.4 GPM
- Copper immersion elements are field serviceable
- Digital control adjustable within 1 degree
- Largest review base in our set at 2185 ratings
Cons
- Highest 1-star share among the whole-unit models we reviewed at 11 percent
- Needs a 240V dedicated double-pole circuit and real panel capacity
- 18.25 inch cube body is the bulkiest in the roundup
For a condo owner replacing a 40-gallon tank, this is the model we recommend. It delivers up to 4.4 GPM, the highest flow in our set, and at 18kW it can keep two showers running without the temperature collapse that plagues smaller units. The exterior digital thermostatic control holds temperature within a degree, which matters more in practice than any spec on the sheet.
Rheem uses two field-serviceable copper immersion heating elements, and that is a real advantage in an apartment where a failed element means waiting on a parts shipment. The unit ships as a stainless steel body on bottom 3/4 inch NPT connections that are threaded for easy replacement, and it runs at 99.8 percent efficiency with no standby losses.
With 2185 ratings it is by far the most reviewed model here, sitting at 4.2 stars. That number is pulled down by an 11 percent one-star share, the highest of the whole-unit models we reviewed, which points to a real tail of owners who hit temperature instability or outright failure. The four- and five-star owners consistently single out the digital control and how easy the elements are to swap.
Size is the practical catch. At 14.5 inches wide by 18.25 inches tall and 18.25 inches deep, this is a near-cube, and it is the bulkiest body in the roundup. Apartment closets that comfortably held a round tank may not have 18 inches of depth to spare against a stud wall.
Electrical demand is the other one. Eighteen kilowatts on 240V puts this unit in the 75A range and demands a dedicated double-pole circuit, and in a building with a 60A service this heater simply is not an option. Confirm the panel before you fall in love with the flow rate.
Verify your panel can handle a 75A class circuit
Have an electrician read the main breaker rating and the number of free spaces in the panel before you order. A 100A panel with a nearly full bus can be a bigger problem than the heater itself, and adding a double-pole breaker consumes two adjacent slots.
Ask for the amperage on the spec sheet in writing. Forum installers describe units that pull up to 91A at full output, and a panel quietly overloaded by a contractor who skipped the upgrade is a recurring and expensive failure mode.
Where the RTEX-18 earns its place
This is the pick for a two-bathroom condo owner with a 200A panel who wants to retire a 40-gallon tank. Reviewers who came from storage tanks highlight the flow and the space saving, and Rheem brands in this category have a long record of years-long daily use on owner forums.
For a one-bath apartment, the RTEX-13 below covers the same demand for less power. We would not pay the extra amperage for 18kW in a single-bath unit.
3. Rheem RTEX-13 13kW Tankless – Best Value for One-Bathroom Units
Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
240V 13kW at 54A
Up to 3.17 GPM
8.25W x 12.62H x 0.5D inch
1/2 inch side connections
LED control
Pros
- 13kW is well matched to a one-bathroom apartment
- 54A draw fits more panels than an 18kW unit
- Only 0.5 inch deep
- Includes a 1.5 GPM water-saving shower head
- Copper immersion elements are field serviceable
Cons
- Cannot run two full showers at once
- Needs a 54A branch circuit
- Published flow figures vary between listings
Thirteen kilowatts is the sweet spot for most one-bedroom apartments, and this is the model we would put in almost any of them. It draws 54 amps on 240V, which is a materially lighter ask than the 75A class units, and the manufacturer-rated flow of 3.17 GPM is enough for one shower plus a sink in most homes.
Two details set it apart. The box includes a 1.5 GPM water-saving shower head, which matters because pairing a low-flow head with a mid-size heater is the single easiest way to get comfortable output from 13kW. Second, the body is 0.5 inches deep, so it mounts flat against a wall or in a shallow closet without eating into the room.
Water connections enter from the sides through 1/2 inch compression fittings, with 1/2 NPT adapters included, which is far easier in a finished apartment than re-piping a floor. The external digital control adjusts in 1 degree increments, so you can dial output to match a particular shower valve.
Owners report consistent temperature and very little maintenance, and the listing carries 74 percent five-star ratings with only 8 percent one-star across 1408 reviews. The recurring caveat is honest: 13kW is a mid-size unit, and buyers who size it against a two-shower household will feel the limit.
One thing to watch is that published flow rates vary between listings, and the 4.8 GPM figure that appears in some product descriptions does not match the manufacturer-rated 3.17 GPM. Take the lower number as your planning figure.
Pair it with a low-flow shower head before you upgrade power
Before moving up in kilowatts, swap the shower head. A 2.0 GPM head paired with this unit frequently performs like a much larger heater, and the included 1.5 GPM head goes further. The saving is real on the power draw, which is the constraint in an apartment.
Plumbers on plumbing and HVAC forums make this point repeatedly: most electric tankless heaters are point-of-use products, not whole-home products. Sizing honestly against the fixtures you actually use is the difference between a good install and a disappointing one.
Who should choose something else
Two full bathrooms running at once will exhaust 13kW. If your condo has two showers and you expect guests, step up to an 18kW model and accept the larger circuit.
Also consider the CAMPLUX 120V option if your building has no spare 240V capacity at all. A modest sink heater beats an install that cannot be permitted.
4. ThermoMate ET180 18kW Tankless – Best Element Design in Hard Water
Tankless Water Heater Electric 18kW at 240 Volt, ThermoMate On Demand Instant Hot Water Heater Up to 4.4GMP, Self-Modulating Energy Saving for Residential Indoor Shower, Draw 76Amp
240V 18kW up to 76A
Two 40A double-pole breakers
17.12W x 13.12H x 3.12D inch
Up to 4.4 GPM
ETL certified
Pros
- Heating element is physically separated from the water tube
- Only 3.12 inches deep despite 18kW
- Digital display adjustable from 80 to 140 degrees in 1 degree steps
- Reviewers report lower water heating costs after switching from a tank
Cons
- Needs two double-pole 40A breakers totaling about 80A
- Some owners report temperature cycling between very hot and lukewarm
- Weight is not published in the spec listing
Hard water is the durability issue that never shows up in most roundups, and this is the model designed around it. The heating element is separated from the water tube rather than sitting in the flow path, which is exactly the design choice that reduces mineral scale buildup and the corrosion that eats copper immersion heaters in hard-water regions.
It is also the flattest 18kW unit we tested at 3.12 inches deep, which matters in a shallow closet. The body measures 17.12 inches wide by 13.12 inches tall, and the digital display adjusts from 80 to 140 degrees F in single-degree steps. Water connects through a 3/4 inch NPT fitting.
Electrical demand is the price of that power. This unit draws up to 76 amps and requires two double-pole 40A breakers on two 8AWG circuits, so it consumes four panel spaces. That is a lot to ask of a 60A apartment service, and homeowners asking on r/AskElectricians frequently get told to check their panel capacity before anything else.
At 4.3 stars across 756 ratings with 70 percent five-star, the dominant positive theme is whole-unit performance and lower energy use than a storage tank. Several reviewers describe a successful swap from a 30A tank heater onto dual 40A breakers, which is the exact upgrade path a condo owner is likely to take.
The clearest negative theme is temperature regulation. One detailed one-star review describes on/off-style swings that persisted through a manufacturer replacement, and another notes that published GPM figures run optimistic at higher flow. If precise temperature matters to you, test the set point before committing.
Ask your building about hard water before you buy any electric heater
Plumbers across the forums rank scale and mineral buildup as the most common long-term complaint with electric tankless units, and a separated-element design like this one directly addresses it. Ask the property manager whether the building treats its water, and if not, budget for annual descaling.
Units with copper immersion elements, including several in this roundup, are more exposed to the same issue. Element type is a durability decision, not a cosmetic one.
Decide whether the panel can spare four slots
Two double-pole breakers take four spaces in the panel and roughly 80A of connected load. A 60A multi-family service cannot support this heater legally, and even a 100A panel needs a load calculation, not a guess.
If your panel is tight, the SIVUATEK later in this guide runs on a single 60A breaker, which is a materially easier conversation with a property manager.
5. EcoSmart ECO 8 – Best Low-Draw 240V Option
EcoSmart ECO 8 Tankless Water Heater, Electric, 8-kW – Quantity 1, 12 x 8 x 4
240V 8kW
Rated flow 2 GPM
8W x 11.5H x 4D inch
4.8 pounds
Stainless steel internals
Pros
- Very compact 8 by 11.5 inch body
- Modulating thermostat holds temperature steadier than on/off heaters
- Stainless steel heat exchanger with in-flow temperature sensors
- Lifetime warranty on electronics
- exchanger and element
Cons
- 2 GPM rated flow means output drops above roughly 1 GPM
- Opening the sealed case to make electrical connections voids the lifetime warranty
- No gravity drain
- so it is a poor choice for a unit that needs winterizing
Eight kilowatts is the smallest 240V option here, and the ECO 8 exists for apartments with a single bathroom and a tight closet. At 8 inches wide by 11.5 inches tall and 4 inches deep, it is one of the smallest modulating units available, and it weighs under 5 pounds.
The modulating thermostat is the real story. Owners credit it with holding output temperature in a narrow band even with a single-handle shower valve, which is the specific failure mode of cheaper on/off heaters. Inlet and outlet sensors sit inside the water flow, so the unit reacts faster than surface-mounted sensors.
Stainless steel covers the heat exchanger and the water-side components, and Rheem-style scale protection is built in. There is a lifetime warranty on the electronics, exchanger and element, though the manufacturer states it covers the cost of the heater only, not labor or incidental damage, and requires professional installation.
Two cautions deserve attention. First, the rated flow is 2 GPM, and above roughly 1 GPM owners report the element cutting out and the water going cold. Second, and less obvious, the electrical connections are internal, so making them means opening the sealed case, which voids the advertised lifetime warranty on the part you most want covered.
Reviewers do document successful installs on a single 40A breaker, and the 4.2-star average across 709 ratings with 70 percent five-star shows a generally satisfied base. There are also reports of leaking at the threaded connections during install, which is a fitting problem rather than a unit problem if caught early.
Understand what the lifetime warranty actually covers
The wording is specific: electronics, exchanger and element, heater cost only, professional installation required. If a handyman opens that case to land the wires, the seal is broken and the coverage is gone. That single fact should push you toward a licensed electrician.
Owners in hard mineral water also report needing to replace the electrode every couple of years. If your building has untreated hard water, factor that into a 15-20 year lifespan assumption.
Where 2 GPM is genuinely enough
A single bathroom with a low-flow shower head and one sink is the use case this unit was built for. Paired with a 1.5 or 2.0 GPM shower head, 2 GPM of rated flow becomes comfortable rather than marginal.
Two fixtures at once is where it falls apart. If you have a second bathroom, the RTEX-13 is the step up, not the ECO 8.
6. WINTEMP WN18 18kW WiFi Tankless – Best for WiFi Temperature Control
WINTEMP 18kW Electric Tankless Water Heater 240V ETL Certified WiFi
240V 18kW up to 75A
Two 40A double-pole breakers
11.1W x 19.2H x 4D inch
4.3 GPM maximum
2-year warranty
Pros
- WiFi temperature adjustment from a phone is unusual in this class
- 18kW and 4.3 GPM covers two to three bathrooms in mild climates
- Only 4 inches deep
- Self-modulating power reduces draw at low flow
Cons
- 75A draw often forces a panel upgrade in an apartment
- Only a 2-year manufacturer warranty
- ABS housing rather than stainless steel wetted parts
The WINTEMP is the newest listing here and the only one with phone-based control, which is genuinely useful in an apartment because you can set the outlet temperature before you get out of bed. Output adjusts remotely, and the self-modulating element drops consumption when flow falls, with the manufacturer claiming up to 99 percent energy savings at low flow.
It delivers 18kW and up to 4.3 GPM, which covers two to three bathrooms in mild climates where incoming water is not already cold. The body is 11.1 inches wide by 19.2 inches tall and 4 inches deep, and it weighs 12 pounds, so the height is the dimension to check against your closet.
It carries ETL certification with leakage, overheat and dry-fire protection, and water connects through a 3/4 inch NPT fitting. Maximum output temperature is 140 degrees F at 130 psi working pressure.
The rating distribution is one of the cleanest in our set at 4.4 stars with 75 percent five-star and 8 percent one-star, but the sample is only 202 reviews, so treat the consensus as encouraging rather than settled. Owners highlight the WiFi control and the space saving over a tank.
The electrical requirement is the recurring practical caution: two 40A double-pole breakers on 8/2 AWG wiring, with 150A household service recommended by the manufacturer. In an apartment with a 60A service, this is not an installable product regardless of how good the app is.
Check the closet height before you fall for the app
At 19.2 inches tall, this is one of the taller bodies in the roundup. Apartment utility closets with a stacked washer and dryer above the water heater are the classic failure case, and the height is the first thing to measure.
Also confirm maximum pressure at your building’s supply. This unit is rated to 130 psi, which is below the 150 psi rating several competing models carry.
Who should pass on this one
Anybody in a small-panel building should pass. The 75A draw and the 150A service recommendation put it out of reach for the tightest apartments, which are exactly the units this guide is written for.
Buyers who want long coverage should also weigh the two-year warranty against the seven-year leakage coverage the Stiebel Eltron later in this list carries.
7. Eemax EEM24013 13kW Tankless – Best Compact Stainless Steel Build
Eemax EEM24013 Electric Tankless Water Heater, Blue
240V 13kW
8W x 11.5H inch wall-mount
99.8 percent efficiency
Self-modulating
Digital display
Pros
- Very clean rating distribution with only 6 percent one-star
- Stainless steel construction throughout
- Same compact 8 by 11.5 inch footprint as the ECO 8
- Self-modulating control for consistent output
- Digital display with adjustable settings
Cons
- 13kW limits simultaneous high-flow fixtures
- Warranty is 5 years for leaks but only 1 year for parts
- Review volume and size availability trail the category leaders
Eemax builds quietly and simply, and that shows in the ratings. At 4.4 stars with 72 percent five-star and only 6 percent one-star, this has the lowest one-star share of any 240V unit in our set. The self-modulating element adjusts energy input to match demand, and the digital display lets you adjust the set point rather than living with a fixed output.
The footprint is 8 inches wide by 11.5 inches tall, identical in outline to the ECO 8, and the body is stainless steel rated at 99.8 percent efficiency for indoor wall-mounted installation. There is no venting requirement and no combustion, which keeps it compliant in a building where gas appliances are not permitted.
Warranty coverage is the weak point, and it is worth reading carefully. The manufacturer provides 5 years for leaks but only 1 year for parts, so a failed element or control board falls into the one-year bucket. That is a real gap for a 15-20 year appliance.
Because the review base is 318 ratings rather than the 2000-plus of the Rheem listings, treat the consensus as favorable but based on a thinner sample. Sales rank also trails the category leaders, so availability across sizes varies more than with the bigger brands.
Owners who do review it point to consistent temperature, low maintenance and a small footprint. There are no widespread failure themes, which for a 13kW stainless unit is the outcome you want to see.
Decide what warranty length is worth to you
Five years of leak coverage is respectable, but one year of parts coverage means most component failures land on you. If you are staying in the apartment beyond five years, factor replacement cost into the decision or favor a longer-warrantied model.
We would not fault the construction here. The question is purely financial: you are buying a smaller warranty on a well-regarded machine.
Know that 13kW is a one-bathroom rating
The same power limit applies here as with the RTEX-13: one shower plus a sink is comfortable, two showers at once is not. Pair it with a 1.5 to 2.0 GPM shower head and the output feels larger than the number suggests.
If your unit is a rental, a self-modulating heater that holds a steady temperature is easier to live with day to day than an on/off model, and that is where this one earns its place.
8. Stiebel Eltron Tempra 20 Trend 19.2kW – Best for Silent Operation
Stiebel Eltron Tempra 20 Trend Electric Tankless Water Heater, 19.2kW, 240V
240V 19.2kW
80A across two 40A breakers
125A service minimum
16.63W x 14.5H x 4-5/8D inch
16.1 pounds
Pros
- Highest rated model in our set at 4.5 stars with 80 percent five-star
- Solid copper heating system made in Germany
- Completely silent with no combustion noise
- 7-year leakage and 3-year parts warranty
- Output adjustable from 68 to 140 degrees F
Cons
- Requires a 125A minimum electrical service
- Rated flow of 2.01 GPM is modest for 19.2kW of power
- Review base of 103 ratings is the thinnest here
If your utility closet shares a wall with a bedroom, the Tempra 20 Trend is the one we would pick. There is no burner, no fan and no combustion, so operation is entirely electronic and effectively silent. The heating system is solid copper with auto-modulation, and output adjusts from 68 to 140 degrees F without a pilot or ignition cycle.
At 4.5 stars with 80 percent five-star and no three-star ratings at all, it is the highest-rated model in this roundup. The build quality is consistently the thing owners mention, along with the German manufacturing and the 7-year leakage plus 3-year parts warranty, the longest coverage in the group.
The electrical demand is where most apartment buyers stop. This unit draws 80 amps across two 40A breakers and Stiebel Eltron specifies a minimum recommended electric service of 125A. That is above the 100A single-family minimum and well above the 60A allowed for a multi-family dwelling.
The body measures 16.63 inches wide, 14.5 inches tall and 4-5/8 inches deep, and it weighs 16.1 pounds, so plan the mounting with two people or a bracket. It needs no venting, which is the main reason it makes sense in a unit without a gas line.
Confirm 125A of service exists before you fall for the rating
Have the panel rating read, not estimated. A 100A building service or a 60A multi-family service cannot legally host this heater, and no amount of product quality changes that. The manufacturer states the minimum explicitly, which saves you from a bad discovery after ordering.
If the panel is 100A and a load calculation supports it, confirm with a licensed electrician. A 200A service upgrade in a condo is a bigger project than the heater itself.
Understand the flow number before you buy
Despite 19.2kW of power, the rated flow is 2.01 GPM, which is modest. That figure reflects a higher temperature rise assumption than most apartments see, so treat it as a planning number and expect real-world flow to drop as inlet water gets colder in winter.
The manufacturer cites energy savings of up to 34 percent in whole-home use, which is a real but not dramatic figure. It is the build and the silence that justify this model, not the flow rate.
9. CAMPLUX 3.5kW 120V Tankless – Smallest Model for the Tightest Closet
CAMPLUX Electric Tankless Water Heater, 3.5kW at 120 Volts Point of Use Water Heater with Self Modulating Technology, Must HardWird Requiring 10AWG Wire
120V 3.5kW
32A breaker and 10AWG wire
7.8W x 6.3H x 3.9D inch
3 pounds
2-year warranty
Pros
- Smallest and lightest model here at 3 pounds and 7.8 inches wide
- Runs on 120V with a 32A breaker and no 240V upgrade
- Self-modulating control holds temperature without hunting
- ETL listed with separated water and electric lines
Cons
- Single-sink point-of-use only
- Must be hardwired with no plug
- 22 degree rise at 1 GPM means lukewarm output at higher flow
- Some owners report underperforming against expected volume
This is the smallest thing in the roundup and the easiest to hide. At 7.8 inches wide, 6.3 inches tall, 3.9 inches deep and 3 pounds, it fits inside a bathroom vanity or a kitchen cabinet that has already lost space to a disposal. A 32A breaker on 10AWG wire is a modest electrical ask, and it is still 120V.
Self-modulating power input adjusts automatically, with the manufacturer claiming up to 98 percent energy savings compared with a continuously heating tank. Water and electricity lines run separately through the body to limit scale and leakage, and the unit is ETL listed with leakage and overheat protection.
Here is the honest limitation. Temperature rise is 22 degrees F at 1.0 GPM, so under that flow you get water at 73 degrees F and above at the tap, which is a cold-ish start in winter but acceptable for handwashing and dish loading. Above 1 GPM it drops toward lukewarm fast.
The rating profile backs that up. With 72 percent five-star and 10 percent three-star, the highest mid-tier share in the group, owners consistently credit steady temperature and easy installation. Every one to three star review reflects the same limit: it cannot deliver hot water for anything beyond one low-flow point.
It is hardwired despite running on 120V, which surprises people who assume a small unit means a plug. Plan for an electrician, and note the 2-year limited warranty. Maximum rated temperature is 131 degrees F at 150 psi working pressure, and connections are 1/2 inch NPT.
Minimum activation flow is 0.4 to 0.66 GPM, so it fires reliably at a normal handwashing flow rate. That makes it a good companion to a bathroom sink where a shower is not in the equation.
Measure the cabinet cavity, not the cabinet
With a 3.9 inch depth and 6.3 inch height, this clears most vanities once you account for the drain trap and supply lines. Bring a tape measure to the cabinet, not the exterior dimensions on the listing, and check the clearance the manual requires around the body.
If you plan two of these in one apartment, the lower electrical cost adds up quickly. A 32A 120V circuit is much easier to justify in a 60A multi-family panel than a 40A 240V circuit, let alone two of them.
Know exactly what it can do
Treat this as a handwash and prep sink heater. It will not run a shower, it will not run two sinks, and the 22 degree rise means flow discipline matters more than the set point.
Buyers expecting a shower on this circuit should choose the 13kW or 18kW 240V models instead, and confirm their panel can carry them first.
10. SIVUATEK 14kW Tankless – Best Single-Breaker 240V Fit
14kW Tankless Water Heater Electric 240V, Sink & Shower,Gray
240V 14kW
Single 60A breaker
Up to 3.3 GPM
12.2W x 17.25H x 15.87D inch
ETL certified
Pros
- Only a single 60A breaker of any 240V model here
- LED readout shows inlet and outlet temperature plus GPM and kW
- Water and electricity are separated to reduce scale
- Wiring accessible without disassembling the housing
- Flexible under-sink or on-wall mounting
Cons
- Maximum output temperature capped at 131 degrees F
- 3.3 GPM falls short of the 18kW models for two full showers
- Review base of 136 ratings is small
The single most valuable thing about this model is its electrical simplicity. Where most 18kW heaters demand two double-pole breakers and four panel spaces, the SIVUATEK 14kW runs on one 60A circuit. In an apartment building, that single fact moves it from impossible to routine.
It delivers up to 3.3 GPM at 99.8 percent thermal efficiency, and the manufacturer cites up to 50 percent lower water heating cost. The LED display is unusually informative for this class, showing inlet and outlet temperature, live GPM, and the kW the element is currently drawing, which makes it easy to see what your fixtures actually demand.
Setpoint runs from 86 to 131 degrees F in single-degree steps. The setpoint cap is a genuine limitation in cold climates, where a higher maximum would be more useful, but in a temperate apartment it is rarely the deciding factor.
Why one breaker changes the conversation with a landlord
Ask any property manager about a two-circuit 18kW heater and you will hear about a panel upgrade. Ask about a single 60A 240V circuit and the answer is usually a load calculation and a licensed electrician. That is a completely different project with a much smaller footprint in a building you do not own.
Another practical advantage: the housing does not need to be opened to make the wiring connections, so the installation is faster and the certification seal stays intact. That concern voids warranties on some competing units.
What the tradeoff is
At 3.3 GPM, this unit sits below the 18kW models when two showers run at once. For a one-bath apartment or a two-bath condo where showers are not simultaneous, that is rarely the difference in daily use.
The 136-review base is thin, and 15.87 inches of depth is not the slimmest body here. Measure the closet, and read the display in person if you can.
What Size Electric Tankless Water Heater Do I Need for an Apartment?
Size an apartment heater by counting fixtures, not square footage. A studio with one sink and a low-flow shower needs far less power than a two-bedroom with two bathrooms, and the difference is usually a step in kW and a step in breaker size rather than a different category of appliance.
The other half of sizing is temperature rise. Manufacturers rate flow at a 35 to 45 degree rise, but real apartments often see a 60 degree rise in winter when incoming water is cold. A unit that delivers 3 GPM at a 45 degree rise will deliver noticeably less at 65 degrees, so oversize slightly if your building has cold supply.
Here is the matching matrix. It is a starting point, not a substitute for a load calculation.
Studio, one bathroom, one sink: 3.5 to 8kW, one fixture at a time, 32A or 40A 120V circuit or a single 240V breaker. Sample picks: CAMPLUX 3.5kW and CAMPLUX 4.5kW.
One-bedroom, one full bathroom plus a kitchen sink: 13 to 14kW, 2 to 3.3 GPM, a single 54A to 60A 240V double-pole breaker. Sample picks: Rheem RTEX-13, Eemax EEM24013, SIVUATEK 14kW.
Two-bedroom condo, two bathrooms, tank replacement: 18 to 19.2kW, 3.2 to 4.4 GPM, two double-pole 40A breakers and a 125A to 200A service. Sample picks: Rheem RTEX-18, ThermoMate ET180, Stiebel Eltron Tempra 20 Trend.
Intermittent or seasonal use unit: avoid the highest kW tiers. Tankless heaters in a unit that sits empty for months hold no water, which is fine for plumbing, but a 19.2kW model that can never reach its rated flow will just run constantly at high draw.
Adding a second point-of-use unit instead of upgrading one central heater is worth serious consideration. Two small 120V heaters on separate circuits often cost less in electrician time and panel impact than one 18kW unit, and they warm up faster at each fixture because the water travels a shorter distance.
Why an Apartment Electrical Panel Matters More Than a House Panel
Apartment panels are smaller by code and by history. NEC 230.79 permits a multi-family dwelling to have an electrical service as small as 60 amps, while a one-family dwelling requires 100 amps. That is not a technicality. It means a building that feels perfectly adequate to a homeowner may have less spare capacity than the equivalent house.
Continuous loads, which includes electric water heating, are commonly evaluated at 125 percent of the heater’s rated draw. A 75A class heater therefore needs roughly 94A of available capacity before anything else in the apartment is counted, which is why a load calculation is not optional in a small panel.
Here is what each class of unit asks of your panel:
120V point-of-use (3.5kW and 4.5kW): a 32A or 40A 120V circuit. The easiest electrical conversation in this guide.
8kW 240V: one 40A double-pole circuit, two panel spaces.
13kW 240V: a 54A branch circuit, two panel spaces.
14kW 240V: a single 60A double-pole breaker, two panel spaces.
18kW 240V: roughly 75A, typically two 40A double-pole breakers, four panel spaces, and a 150A service recommendation on some models.
19.2kW 240V: 80A across two 40A breakers, with a 125A minimum service requirement.
One warning from the forums deserves repeating here. Installers have described contractors who added two 40A breakers to a panel that was never actually upgraded, then called the job finished, leaving the service still at 100 amps. If your install requires a panel change, ask to see the panel label and the permit before the walls close.
Do You Need Your Landlord’s Permission?
Renters should assume the answer is yes. A water heater is a permanent plumbing and electrical change, and in most leases that is a structural modification requiring written approval. Condo owners have a different problem: the association may control shared mechanical spaces, common-area electrical panels, and any work that touches a shared wall or riser.
Before you email anyone, gather four facts. The main breaker rating of your panel, the free space in the panel, the amperage the model requires, and whether the unit is gas or electric. That single paragraph answers most of what a property manager will ask.
Here is the script we would send:
What is the rating of the electrical panel serving my unit, and who owns it?
Are there free breaker slots, and has anyone assessed the load on the existing circuits?
Does the lease or the association require written approval and a licensed contractor for water heater work?
Is the existing water heater fed from a shared system, or is it dedicated to my unit?
If the answer to the first question is 60 amps, the practical path is a 120V point-of-use unit on a small circuit, or two of them, rather than any 240V model in the upper tiers. We covered the space side of apartment life in our storage beds for studio apartments guide, and the same measure-the-space-first logic applies to mechanical equipment.
Hard Water, Maintenance and What It Costs to Run
Mineral scale is the durability issue that decides how long these units last. Hard water leaves deposits on heating elements and inside copper heat exchangers, which insulates the element, forces the unit to draw more power for the same output, and eventually kills the element. Most manufacturers expect 15 to 20 years of service in treated water and considerably less in heavily hard water.
Ask the property manager whether the building softens its water. If it does not, favor models with a separated element or stainless steel water-side parts, and plan on descaling annually. The ThermoMate later in this guide is the clearest example of the separated-element approach.
Standby losses are the other real efficiency story. A storage tank burns energy continuously to keep water hot; a tankless heater draws power only when a tap opens. That difference is why these units are frequently cited as cutting water heating costs by 30 to 50 percent, though the actual figure depends entirely on household usage and your utility rate.
The honest math: a studio where one person showers every day will notice a modest reduction. A family running two showers and a dishwasher will notice a large one, because the tank is being reheated all day regardless. Forum threads about operating cost consistently find that usage, not equipment efficiency, drives the bill.
Gas tankless is essentially off the table for most apartments. Even where a gas line exists, venting a combustion heater through an exterior wall is usually prohibited in multi-family construction, and venting up through a roof adds cost and association approval. That is the entire reason the electric category is the only one worth researching in this situation. If you are shopping broadly rather than for a specific constraint, our RV tankless water heater guide covers the same 120V point-of-use logic for a different space.
Frequently Asked Questions
Can you use a tankless water heater in an apartment building?
Yes, and electric is almost always the only viable fuel in an apartment. Most buildings have no gas line and rarely allow venting a combustion heater through an exterior wall. Electric tankless units mount on a wall, need no venting, and heat water only when a tap opens, so they suit apartments with limited space and small panels.
What size tankless water heater do I need for an apartment?
Match it to your fixture count. A studio with one bathroom needs 3.5 to 8kW on a 120V or small 240V circuit. A one-bedroom with a full bathroom plus a kitchen sink needs 13 to 14kW on a single 54A to 60A double-pole breaker. A two-bedroom condo replacing a tank needs 18 to 19.2kW and a 125A to 200A service.
Do I need my landlord’s permission to install a tankless water heater?
If you rent, assume yes. A water heater is a permanent plumbing and electrical change, and most leases treat it as a structural modification requiring written approval. Send your property manager the panel rating, the free breaker space, the amperage your model needs, and whether the unit is gas or electric. That single paragraph answers most of what they will ask.
Why does an apartment’s electrical panel matter more than a house’s?
NEC 230.79 allows a multi-family dwelling to have a service as small as 60 amps, while a one-family dwelling requires 100 amps. Electric water heating is a continuous load, commonly evaluated at 125 percent of rated draw, so a 75A class heater needs roughly 94A of available capacity before any other load is counted. Panel headroom, not flow rate, is the first thing to verify.
What breaker size does an electric tankless water heater need?
It depends on wattage. A 3.5kW 120V unit needs a 32A breaker and a 4.5kW 120V unit needs 40A. At 240V, an 8kW heater needs 40A, 13kW needs 54A, 14kW needs 60A, and 18kW to 19.2kW models need two double-pole 40A breakers totaling 75A to 80A. Larger units also consume two to four panel spaces.
Final Verdict: The Best Electric Tankless Water Heaters for Apartments in 2026
For most apartments, the CAMPLUX 4.5kW 120V point-of-use heater is the pick, because it is the only serious option that sidesteps the 240V question entirely and fits in 2.52 inches of depth. One-bathroom owners with a workable 240V circuit get more from the Rheem RTEX-13 at 13kW and a 54A draw, and condo owners replacing a tank should go to the Rheem RTEX-18 at up to 4.4 GPM.
Whatever you choose, read your panel rating first. The best electric tankless water heaters for apartments are the ones you are permitted to install, and on a 60A multi-family service that answer usually points to 120V.
Once the install is sorted, the other decisions are small: measure the closet, pair any mid-size heater with a low-flow shower head, and check whether your building has hard water. Apartment living is tight on space and electrical capacity, and the right unit for 2026 is the one that fits both without arguing.